Spring中的@Lazy注解用法实例

@Target({ElementType.TYPE, ElementType.METHOD, ElementType.CONSTRUCTOR, ElementType.PARAMETER, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Lazy {
   /**
    * Whether lazy initialization should occur.
    */
   boolean value() default true;
}

package com.dashu.bean;
public class Persion {
    public Persion(String name, int age) {
        this.name = name;
        this.age = age;
    }
    private String name;
    private int age;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "Persion{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

package com.dashu.config;
import com.dashu.bean.Persion;
import org.springframework.context.annotation.*;
/**
 * @Configuration 注解：告诉Spring这是一个配置类
 *
 * 配置类 == 配置文件（beans.xml文件）
 *
 */
@Configuration
public class BeanConfig {
    @Lazy
    @Bean
    public Persion persion(){
        System.out.println("初始化Persion...");
        return new Persion("张三",20);
    }
}

package com.dashu;
import com.dashu.bean.Persion;
import com.dashu.config.BeanConfig;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class Main {
 public static void main(String[] args) {
        AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(BeanConfig.class);
        /**
         * 只在第一次获取Bean时，初始化。之后的获取都是同一个对象
         */
        Persion persion1 = (Persion) annotationConfigApplicationContext.getBean("persion");
        Persion persion2 = annotationConfigApplicationContext.getBean(Persion.class);
        System.out.println(persion1 == persion2);
    }
}